Process for the control of bacteria in water flooding operations



United States My invention relates to the control of bacteria in water flooding operations used in the secondary recovery of petroleum oils, and more particularly, to contro ling such organisms by incorporating into the flooding water amounts of nitrohexahydropyrimidines having the following structural formula:

where R is lower alkyl and where R is selected from the group consisting of lower alkyl and lower hydroxyalkyl.

US. Patent 2,839,467 lists many of the problems found in the secondary oil recovery art and the means whereby some of these problems have been solved. The problem of cont-rolling sulfate reducing bacteria is ever present and always diflicult, as the growth of the microorganisms is not controlled by economically practicable amounts of many bactericides generally utilized in bacterial control and the microorganisms sometimes become resistant to generally used bactericides.

The problems attending the control of microorganisms other than those of the sulfate reducing type are more easily solved but are, nevertheless, present. These microorganisms are generally controlled by moderate amounts 'of known bactericides.

I have now discovered that noxious microorganisms present in water flooding operations are economically controlled by my above-described nitrohexahydropyrimidines. Compounds which I have found to be operative in my process include 1,3-bis-(l hydroxymethylpropyl)--rnethyl-5 -nitrohex ahydropyrimidine, 1,3 ,-bis Z-hydroxyethyl) 5-methyl-5-nitrohexahydropyrimidine, 1,3,5-trimethyl-5- nitrohexahydropyrimidine, 5 ethyl-1,3-dimethyl-5-nitrohexahydropyrimidine, 5 ethyl-1,3-bis(2-ethylhexyl)-5- nitrohexahydropyrimidine, 1,3-dicyclohexyl-S-ethyl-S-nitrohexahydropyrimidine, S-ethyl-l,3-bis(hydroXy-t-butyl)- 5 nitrohexahydropyrimidine, and 5-ethyl-1,3-bis(2-hydroxypentyl) -5-nitrohexahydropyrimidine.

The usual procedure for the treatment of water to be utilized in flooding operations is to produce a concentrate of the bactericide in water and then continuously inject this concentrate into the water to be used in flooding operations at a rate which forms a desired dilution of the bactericide. This is done prior to pumping the water into the oil bearing subterranean formation. Sampling and checking the water for bacteria will show whether the chemical concentration needs to be raised or may be lowered to control effectively all bacterial growth and to eflect an elimination of sulfate reducing bacteria from the water.

Altern-ately, the bacterieides utilized in my process may be added to the oil-bearing formations periodically, for example, once a week as a high potency concentrate or the undiluted bactericide may be injected into the formation.

I have found that the compounds utilized in my process are effective against some strains of bacteria in water at concentrations as low as about 5 ppm. However, I prefer atcnt I to utiilze concentrations in excessof about '10 to ppm. as I have found that even. very resistant strains of sulfate reducing bacteria such as Deswlfovibrio desulfuricans are effectively controlled at these concentrations.

It is to be understood, of course, that not all of the compounds utilized in my process are effective to the same degree. The following table sets out concentrations at which I have found nitrohexahydropyrimidines coming within the scope of my invention to be completely effective against a resistant strain of sulfate reducing bacteria, Desulfovibrio desulfuricans, in water flooding operations.

Eflective Concentration \(p.p.m.) Nitrohexahydropyrimidine: t

1,3 bis(l-hydroxymethylpropyl)-5-methyl- 5 nitrohexahydropyrimidirie 12--25 5 ethyl-1,3-dimethyl-5-nitrohexahydropyrimidine 25-50 5 ethyl-1,3-bis(hydroxy-t butyl)-5-nitrohexabydro pyrimidine 12-25 The following examples illustrate the use of my nitrohexahydropyrimidines for the control of sulfate reducing microorganisms in water flooding operations. It is not intended that my invention be limited to the exact compositions or concentrations shown. Rather, it is intended that all equivalents obvious to those skilled in the art be included within the scope of my invention as claimed.

Example I In a water treatment plant, a water concentrate containing 1,3-bis(l-hydroxymethylpropyl)-5-methyl-5-nitrohexahydropyrimidine is continually added to water to be pumped into a subterranean oil-bearing formation at such a rate that a 25 ppm. solution of 1,3-bis( lhydroxymethyl-propyl) -5-methyl-5 nitrohexahydropyrimidine is formed. The nitrohexahydropyrimidine treated flooding water is pumped into the oil-bearing formation and is completely effective in preventing bacterial plugging of the oil bearing sands and the piping system utilized in the water flooding operations.

Example II Utilizing the process of Example I, I have found that 50 ppm. of S-ethyl-1,3-dimethyl-S-nitrohexahydropyrimidine is effective in controlling sulfate-reducing bacteria in water flooding operations.

Example III Utilizing the process of Example I, I have found that 25 ppm. of 5-ethyl'1,3-bis(hydroxyt-butyll-5-nitrohexahydropyrimidine is efiective in controlling sulfate-reducing bacteria in water flooding operations.

Now having described my invention, what I claim is:

1. In the process of secondary oil recovery characterized by the step of injecting flooding water into oil-bearing subterranean formations to displace portions of the residual oil therein, the improvement comprising having present in said injected flooding water in excess of about 5 ppm. of a nitrohexahydropyrimidine having the following structural formula:

wherein R is lower alkyl and wherein R is selected from the group consisting of lower alkyl and lower hydroxyalkyl.

3 2. In .-a flooding process for the recovery of oil from oil-bearing subterranean formations, the improvement which comprises flooding the oi1-:bearing subterranean formulation with an aqueous liquid containing in excess of about 5 ppm. of a nitrohexahydropyrirnidine having the following structural formula:

wherein R is lower :alkyl and wherein R is selected from the group consisting of lower alkyl and lower hydroxyelkyl.

3. The process of claim 2 wherein the nitrohexahydropyrimidine is 1,3- bis( l-hydroxymethylprcpyl)-5-methy1-5- nitrohexahyd-ropyrimidine.

4. The process of claim 2 wherein the nitrohexahydropyrimidine is 1,3,5-trimethyl-5-nitrohexahydropyrimidine.

5. The process of claim 2 wherein the nitrohexahydropyrimidine is S-ethyl-l,3-dimethyl-5-nitrohexahydropyrimidine.

6. The process of claim 2 wherein the nitrohexahydropyrimidine is 5-ethyl-1,3 bis(hydroxy-t-buty1)-5-nitrohexahydropyrimidine.

References Cited in the file of this patent UNITED STATES PATENTS 2,391,847 Senkus Dec. 25, '1945 2,692,231 Stayner et a1 Oct. r19, 1954 2,837,463 Fosdick et a1 June 3, 1958 2,867,279 Cocks Ian. 6, 1959 2,976,236 Bennett et al Mar. 21, 1961 FOREIGN PATENTS 107,419 Australia May 25, 1939 4211, 189 Italy Mar. 19, 1947 

1. IN THE PROCESS OF SECONDARY OIL RECOVERY CHARACTERIZED BY THE STEP OF INJECTING FLOODING WATER INTO OIL-BEARING SUBTERRNEAN FORMATIONS TO DISPLACE PORTIONS OF THE RESIDUAL OIL THEREIN, THE IMPROVEMENT COMPRISING HAVING PRESENT IN SAID INJECTED FLOODING WATER IN EXCESS OF ABOUT 5 P.PM. OF A NITROHEXAHYDROPRIMIDINE HAVING THE FOLLOWING STRUCTURAL FORMULA: 